1. Field of the Invention
This invention relates primarily to the repair of alloy articles and, more particularly, to a powder mixture for the repair of cobalt base and nickel base superalloys and to the repaired article.
2. Description of the Prior Art
High temperature cobalt base and nickel base superalloys are used in the manufacture of high temperature operating gas turbine engine components including combustors and turbine vanes and blades, among others. During operation of such components under strenuous, high temperature operating conditions, various types of damage or deterioration can occur. For example, cracks can result from thermal cycling, from foreign object impact, etc. Also, such components can experience damage, such as cracks and inclusions, during manufacture. It is well known that the cost of such components of high temperature cobalt base and nickel base superalloys is relatively high. Accordingly, it is more desirable to repair such components than to replace them with new ones.
The repair and cleaning of certain superalloy articles, for example using fluoride ions, is described in U.S. Pat. No. 4,098,450-Keller et al, issued July 4, 1978, and assigned to the assignee of the present invention. Other methods, particularly useful in connection with cobalt base alloys, include first cleaning the article in a reducing atmosphere such as hydrogen, or mechanically removing damages portions, and then repairing the damaged or cracked portion by vacuum brazing-type techniques. Such methods have used alloy powders or mixtures of powders such as the powder described in U.S. Pat. No. 3,759,692-Zelahy, patented Sept. 18, 1973, or mixtures of powders such as described in U.S. Pat. Nos. 4,381,944-Smith, Jr. et al, patented May 3, 1983 or U.S. Pat. No. 4,478,638-Smith, Jr. et al, patented Oct. 23, 1984.
With the introduction of more recent, higher strength and more highly alloyed superalloys, it has been found that such known alloy systems or mixtures of powders would either not fill or repair the cracks or defects properly, or had less than desirable material characteristics, or seriously affected the parent or substrate alloy.